Don't let AI make you rusty.

Five-minute bug hunts with instant feedback. Right here in your browser, or inside Claude.

Use it in Claude or try it right here ↓

Free. No signup. No catch.

AI writes the code.
Who catches the bugs?

Reading code and judging it is most of the job now. It is a skill like any other, and almost nobody practises it.

1. The job changed

You spend the day reading code you didn't write and deciding whether it's right.

2. Spotting bugs is trained

AI code looks right even when it isn't. Seeing through that comes from reps, not from reading about it.

3. But nothing corrects you

Miss one in review and no red squiggle appears. You never find out, so the blind spot stays.

Reps without a verdict just rehearse your blind spots. So here every answer gets one: right or wrong, straight away, with the reason. Levels go up when you're right, down when you're not.

Even better inside Claude.

SotiTrainer also lives inside Claude, Anthropic's AI assistant. Claude hands you exercises right in the chat and explains every answer, not just pass or fail.

  1. 1

    Open Claude

    Go to claude.ai or open the Claude desktop app and sign in.

  2. 2

    Add SotiTrainer

    Settings → Connectors → Add custom connector. Name it “SotiTrainer” and paste this link:

    A connector is a plug-in that gives Claude a new skill.

  3. 3

    Say “Start Soti”

    In a new chat. The editor appears right in the conversation, and Claude grades what you send.

Questions? Answers.

Yes, it's free.

No account, no ads, no tracking. For the Claude version you need a Claude account that can add custom connectors.

Levels go from 2 to 5.

2 is plain logic, 3 is JavaScript gotchas, 4 is async and edge cases, 5 is security, concurrency and performance. Get one right and you go up, get one wrong and you go down. A session is 5 exercises.

This page checks. Claude explains.

Here, a test says pass or fail. In Claude, the assistant reads your code, tells you why it works or doesn't and picks the next level for you.

No, your code isn't stored.

On this page your code runs in your own browser and goes nowhere. In Claude, your answer stays in your chat. The trainer's server only picks the exercise and never sees what you typed.

Yes, you can write code too.

Switch to “Write” next to the Check button: you get a short task and a function signature and write the rest.

Yes, it's JavaScript only. For now.

Bugs are bugs in every language, but JavaScript has the most creative ones.